Gas sensor

ABSTRACT

A gas sensor includes a light receiving element, a light emitting element, an integrated circuit, a lead frame, and a sealing member configured to seal these into a package. The lead frame includes at least one die pad portion and a plurality of terminal portions, the die pad portion includes a first region having a first thickness and a second region having a second thickness thinner than the first thickness, the integrated circuit is arranged on the second region of the die pad portion, the light emitting element is electrically connected to at least one of the plurality of terminal portions, the light receiving element is electrically connected to the integrated circuit and is arranged on the opposite side to the light emitting element with the integrated circuit interposed therebetween, and the integrated circuit is electrically connected to at least one of the plurality of terminal portions.

TECHNICAL FIELD

The present invention relates to a gas sensor.

BACKGROUND ART

Conventionally, as gas measurement apparatuses for concentrationmeasurement of a gas to be measured in the atmosphere, non-dispersiveinfrared-type optical gas concentration measuring apparatuses configuredto, using a feature that the wavelength of absorbed infrared raysdiffers depending on the type of gas, measure gas concentration bydetecting the amount of absorption of infrared rays have been known.

For example, PTL 1 discloses a gas sensor including a light receivingelement and a light emitting element.

CITATION LIST Patent Literature

PTL 1: JP 2018-136154 A

SUMMARY OF INVENTION Technical Problem

However, the current state is that what form is preferable for a gassensor that, in addition to a light receiving element and a lightemitting element, further includes an integrated circuit configured toperform gas concentration calculation has not been known. In particular,no gas sensor having a small size and enabling high precisionmeasurement has been known.

Accordingly, an object of the present invention is to provide a gassensor having a small size and enabling high precision measurement.

Solution to Problem

A gas sensor according to one embodiment of the present invention is agas sensor including a light receiving element, a light emittingelement, an integrated circuit, a lead frame, and a sealing memberconfigured to seal the light receiving element, the light emittingelement, the integrated circuit, and the lead frame into a package, inwhich the lead frame includes at least one die pad portion and aplurality of terminal portions, at least the die pad portion includes afirst region having a first thickness and a second region having asecond thickness thinner than the first thickness, the integratedcircuit is arranged on the second region of the die pad portion, thelight emitting element is neither electrically connected directly to thelight receiving element nor to the integrated circuit and iselectrically connected to at least one of the plurality of terminalportions, the light receiving element is electrically connected to theintegrated circuit and is arranged on the opposite side to the lightemitting element with the integrated circuit interposed between thelight receiving element and the light emitting element, and theintegrated circuit is electrically connected to at least one of theplurality of terminal portions.

A gas sensor according to another embodiment of the present invention isa gas sensor including a light receiving element, a light emittingelement, an integrated circuit, a lead frame, and a sealing memberconfigured to seal the light receiving element, the light emittingelement, the integrated circuit, and the lead frame into a package, inwhich the lead frame includes at least one die pad portion and aplurality of terminal portions, the light emitting element is neitherelectrically connected directly to the light receiving element nor tothe integrated circuit and is electrically connected to at least one ofthe plurality of terminal portions, the light receiving element iselectrically connected to the integrated circuit and is arranged on theopposite side to the light emitting element with the integrated circuitinterposed between the light receiving element and the light emittingelement, and the integrated circuit is electrically connected to atleast one of the plurality of terminal portions.

A gas sensor according to still another embodiment of the presentinvention is a gas sensor including a light receiving element, a lightemitting element, an integrated circuit, a lead frame, and a sealingmember configured to seal the light receiving element, the lightemitting element, the integrated circuit, and the lead frame into apackage, in which the lead frame includes at least one die pad portionand a plurality of terminal portions, at least the die pad portionincludes a first region having a first thickness and a second regionhaving a second thickness thinner than the first thickness, theintegrated circuit is arranged on the second region of the die padportion, the light emitting element is electrically connected to atleast one of the plurality of terminal portions, the light receivingelement is electrically connected to the integrated circuit and isarranged on the opposite side to the light emitting element with theintegrated circuit interposed between the light receiving element andthe light emitting element, the integrated circuit is electricallyconnected to at least one of the plurality of terminal portions, thefirst region of the die pad portion is arranged at a periphery of thesecond region and is arranged in such a way that the second regionsurrounds a portion of an end of the first region.

A gas sensor according to still another embodiment of the presentinvention is a gas sensor including a light receiving element, a lightemitting element, an integrated circuit, a lead frame, and a sealingmember configured to seal the light receiving element, the lightemitting element, the integrated circuit, and the lead frame into apackage, in which the lead frame includes at least one die pad portionand a plurality of terminal portions, the light receiving element iselectrically connected to the integrated circuit, the plurality ofterminal portions are arranged in line along the die pad portion on bothsides of the die pad portion with the die pad portion interposed betweenthe terminal portions, the integrated circuit is electrically connectedto at least one of the plurality of terminal portions, at least oneterminal portion among terminal portions electrically connected to theintegrated circuit includes a region extending in a second direction,the second direction intersecting a direction in which the plurality ofterminal portions are lined, and a region extending in a firstdirection, the first direction intersecting the second direction andcoming close to the integrated circuit, between the integrated circuitand the light emitting element and includes a bonding region at a tip ofthe region extending in the first direction, and the integrated circuitand the bonding region are connected to each other by a conductive wire.

A gas sensor according to still another embodiment of the presentinvention is a gas sensor including a light receiving element, a lightemitting element, an integrated circuit, a lead frame, and a sealingmember configured to seal the light receiving element, the lightemitting element, the integrated circuit, and the lead frame into apackage, in which the lead frame includes at least one die pad portionand a plurality of terminal portions, at least the die pad portionincludes a first region having a first thickness and a second regionhaving a second thickness thinner than the first thickness, theintegrated circuit is arranged on the second region of the die padportion, the light receiving element is electrically connected to theintegrated circuit, the plurality of terminal portions are arranged inline along the die pad portion on both sides of the die pad portion withthe die pad portion interposed between the terminal portions, theintegrated circuit is electrically connected to at least one of theplurality of terminal portions, at least one terminal portion amongterminal portions electrically connected to the integrated circuitincludes a region extending in a second direction, the second directionintersecting a direction in which the plurality of terminal portions arelined, and a region extending in a first direction, the first directionintersecting the second direction and coming close to the integratedcircuit, between the integrated circuit and the light emitting elementand includes a bonding region at a tip of the region extending in thefirst direction, and the integrated circuit and the bonding region areconnected to each other by a conductive wire.

Advantageous Effects of Invention

An aspect of the present invention enables a gas sensor having a smallsize and enabling high precision measurement to be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a planar schematic diagram illustrative of an example of a gassensor according to a first embodiment of the present invention;

FIG. 2 is another planar schematic diagram illustrative of the exampleof the gas sensor according to the first embodiment of the presentinvention;

FIGS. 3A to 3D are another planar schematic diagram and cross-sectionalviews illustrative of the example of the gas sensor according to thefirst embodiment of the present invention;

FIGS. 4A to 4C are a back surface schematic diagram and cross-sectionalviews illustrative of the example of the gas sensor according to thefirst embodiment of the present invention;

FIGS. 5A and 5B are a schematic diagram viewed from the light reflectionportion side and a cross-sectional view illustrative of an example of agas sensor according to a second embodiment of the present invention;

FIGS. 6A to 6C are a back surface schematic diagram and cross-sectionalviews illustrative of a variation of the gas sensor according to thesecond embodiment of the present invention;

FIG. 7 is a planar schematic diagram illustrative of an example of a gassensor according to a third embodiment of the present invention;

FIG. 8 is a planar schematic diagram illustrative of an example of a gassensor according to a fourth embodiment of the present invention;

FIG. 9 is a planar schematic diagram illustrative of a variation of thegas sensor according to the fourth embodiment of the present invention;and

FIGS. 10A to 10D are flowcharts illustrative of an example of amanufacturing process of the gas sensor according to the firstembodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will now be described withreference to the drawings. In the following description of the drawings,the same or similar reference signs are assigned to the same or similarportions. However, it should be noted that the drawings are schematicand relations between thicknesses and planar dimensions and the like aredifferent from actual ones. The following embodiment indicates devicesand methods to embody the technical idea of the present invention by wayof example, and the technical idea of the present invention does notlimit the materials, shapes, structures, arrangements, and the like ofthe constituent components to those described below. The technical ideaof the present invention can be subjected to a variety of alterationswithin the technical scope prescribed by the claims described in CLAIMS.

First Embodiment

FIGS. 1, 2, 3A to 3D, and 4A to 4C are schematic diagrams illustrativeof an example of a gas sensor according to a first embodiment of thepresent invention. FIG. 1 is a schematic diagram illustrative of anexample of the gas sensor according to the first embodiment and is aplanar schematic diagram viewed from a surface on the mounting surfaceside, which is connected to an external device. Herein, it is assumedthat a surface on the mounting surface side of a gas sensor 1 is thefront surface and a surface on the opposite side thereto is the backsurface. Note that, in FIG. 1 , illustrations of connection wiring and asealing member are omitted for facilitating understanding.

In FIG. 1 , reference signs 1, 10, 20, and 30 indicate the gas sensor, alight receiving element, a light emitting element, and an integratedcircuit, respectively, and reference signs 41 and 42 respectivelyindicate portions of a conductive lead frame 40 and, specifically, thereference signs 41 and 42 indicate a die pad portion and terminalportions, respectively. The die pad portion 41 and the terminal portions42 are separated from each other. In addition, in each of the die padportion 41 and the terminal portions 42, reference signs R1 and R2indicate a first region that has a first thickness and a second regionthat has a second thickness thinner than the first thickness,respectively.

The gas sensor 1 is formed in a rectangle when viewed in plan, and, in acentral portion in the width direction of the gas sensor 1, the die padportion 41, which extends in the longitudinal direction of the gassensor 1, is arranged and, on both right and left sides of the die padportion 41, a plurality of terminal portions 42 are arranged in linealong the die pad portion 41.

The die pad portion 41 has a rectangular portion 41 a that is formed ina rectangle and that extends along the longitudinal direction of the gassensor 1 and projecting portions 41 b that are formed on each of bothedges in the longitudinal direction of the rectangular portion 41 a. Twoprojecting portions 41 b are formed at locations close to the ends inthe width direction of the rectangular portion 41 a with a spaceinterposed therebetween on each edge in the longitudinal direction ofthe rectangular portion 41 a, the projecting portions 41 b on each ofboth edges in the longitudinal direction are formed at locationsequidistant from the central point in the width direction of therectangular portion 41 a, and the ends of the projecting portions 41 breach the edges in the longitudinal direction of the gas sensor 1. Onone end side in the longitudinal direction of a central portion in thewidth direction of the rectangular portion 41 a, a rectangular opening41 c for arranging the light receiving element 10 (hereinafter, referredto as a light receiving element arrangement region) is formed, and, onthe other end side, a rectangular opening 41 d for arranging the lightemitting element 20 (hereinafter, referred to as a light emittingelement arrangement region) is formed.

The terminal portions 42 have the same shape and are formed in anelongated rectangular shape, and the respective terminal portions 42have one ends arranged in line at equal intervals along either of thelong sides of the rectangular portion 41 a in such a manner as to faceeither of the long sides with a constant gap interposed therebetween andthe other ends formed in such a manner as to reach either of the edgesin the width direction of the gas sensor 1. The terminal portions 42 onthe right and left sides with the die pad portion 41 interposedtherebetween are arranged in line symmetry about the central lineextending in the longitudinal direction of the gas sensor 1.

The rectangular portion 41 a of the die pad portion 41 and a region ofeach of the projecting portions 41 b, the region continuing to therectangular portion 41 a and occupying approximately one-third of thewhole of the projecting portion 41 b, form a second region 41(R2) havingthe second thickness. A region of each of the projecting portions 41 b,the region being the projecting portion 41 b excluding the second region41(R2) and being on the opposite side to the rectangular portion 41 a,forms a first region 41(R1) having the first thickness. A region of eachof the terminal portions 42, the region being a region close to therectangular portion 41 a and being slightly smaller than a half of thewhole of the terminal portion 42, forms a second region 42(R2) havingthe second thickness. A region of each of the terminal portions 42, theregion being the terminal portion 42 excluding the second region 42(R2),being on the opposite side to the rectangular portion 41 a, and beingslightly larger than a half of the whole of the terminal portion 42,forms a first region 42(R1) having the first thickness.

The light receiving element 10 is arranged in a light receiving elementarrangement region 41 c, and the light emitting element 20 is arrangedin a light emitting element arrangement region 41 d. In other words, thelight receiving element 10 and the light emitting element 20 arearranged at locations the peripheries of which are surrounded by thesecond region 41(R2) of the die pad portion 41. The integrated circuit30 is arranged at the center in the width direction of the rectangularportion 41 a slightly on the light receiving element 10 side of thecenter in the longitudinal direction of the rectangular portion 41 a. Inother words, the integrated circuit 30 is arranged on the second region41(R2) of the die pad portion 41.

As illustrated in FIGS. 3A to 3D, which will be described later, bydisposing a sealing member 80 in such a manner as to contain the wholeof the lead frame 40 within the outer shape thereof, the gas sensor 1 ispackaged in a substantially rectangular parallelepiped shape.

Note that, although, in FIG. 1 , one integrated circuit 30 is arrangedon the second region 41(R2) of the die pad portion 41, the gas sensor 1may include a plurality of integrated circuits 30 and the plurality ofintegrated circuits 30 may be arranged on the second region 41(R2) ofthe die pad portion 41.

FIG. 2 is a diagram illustrated by adding electrical connectionrelationships to the planar schematic diagram of the gas sensor 1illustrated in FIG. 1 . In gas sensor 1, electrical connections areachieved by using conductive wires LW.

As illustrated in FIG. 2 , the light emitting element 20 has twoterminals on each of both sides of the light emitting element 20 alongthe longitudinal direction of the die pad portion 41. The respectiveterminals of the light emitting element 20 are connected to, among theplurality of terminal portions 42 arranged along the longitudinaldirection of the die pad portion 41, in total four terminal portions 42that are composed of two terminal portions 42 on each of the right sideand the left side, the two terminal portions 42 being arranged on theside where the edge of the gas sensor 1 on the light emitting element 20side is located. The respective terminals of the light emitting element20 are connected only to the second regions 42(R2) of the terminalportions 42, and the terminals and the second regions 42(R2) aredirectly connected to each other by conductive wires LW. The lightemitting element 20 is neither directly connected to the light receivingelement 10 nor to the integrated circuit 30. As used herein, the terms“directly connected” mean being connected only by one conductive wireLW.

The light receiving element 10 has a terminal on each of the right endside of an edge on the integrated circuit 30 side and the left end sideof an edge on the opposite side to the integrated circuit 30, asillustrated in FIG. 2 . The light receiving element 10 is connected onlyto the integrated circuit 30, and the respective terminals of the lightreceiving element 10 are connected to two terminals that are disposed onan edge portion on the light receiving element 10 side of the integratedcircuit 30, by conductive wires LW.

As illustrated in FIG. 2 , the integrated circuit 30 has, for example,in total twelve terminals that are composed of six terminals on each ofthe right edge side and the left edge side of the integrated circuit 30and also has two terminals on the light receiving element 10 side. Thetwelve terminals formed on the right and left sides of the integratedcircuit 30 are respectively connected to, among the plurality ofterminal portions 42 arranged on both sides of the die pad portion 41along the longitudinal direction thereof, in total twelve terminalportions 42 that remain after excluding the terminal portions 42connected to the light emitting element 20. Specifically, the terminalsformed at the right and left edges of the integrated circuit 30 areconnected to the second regions 42(R2) of the terminal portions 42 byconductive wires LW. The second region 42(R2) of each terminal portion42 serves as a bonding region 42(R3). The thickness of the bondingregions 42(R3) are not limited to a specific value as long as beingthinner than the thickness of the first regions 42(R1). There are somecases where, from a viewpoint of process easiness, the thickness of thebonding regions 42(R3) are preferably the same as the thickness of thesecond region 41(R2) of the die pad portion 41, as illustrated in FIG. 2.

Note that the bonding regions 42(R3) (that is, the second regions42(R2)) may have surfaces thereof subjected to plating.

FIGS. 3A to 3D are diagrams illustrated by adding the sealing member 80to the gas sensor 1 illustrated in FIG. 2 , and FIG. 3A is a schematicdiagram of the gas sensor 1 in plan view. FIGS. 3B, 3C, and 3D arecross-sectional schematic diagrams taken along the lines A-A′, B-B′, andC-C′ in FIG. 3A, respectively.

As illustrated in FIGS. 3A to 3D, the sealing member 80 is formed insuch a manner as to cover an area excluding the first regions 41(R1) and42(R1) of the lead frame 40 and including the light receiving element10, the light emitting element 20, the integrated circuit 30, theconductive wires LW, and the second regions 41(R2) and 42(R2) of thelead frame 40 and to be flush with the surfaces of the first regions41(R1) and 42(R1) of the lead frame 40.

It can be understood that, as a result, in the planar schematic diagramillustrated in FIG. 3A, the surface of the gas sensor 1 in plan view,that is, the surface located on the upper side in the cross-sectionalschematic diagrams illustrated in FIGS. 3B to 3D, is in a state in whichonly the sealing member 80, the first regions 41(R1) (not shown) of thedie pad portion 41, and the first regions 42(R1) of the terminalportions 42 are exposed.

FIG. 4A is a back surface schematic diagram illustrating the gas sensor1 illustrated in FIGS. 3A to 3D that is viewed from the back side, thatis, the side where a surface from which a portion of each of the lightreceiving element 10 and the light emitting element 20 is exposed islocated. FIGS. 4B and 4C are cross-sectional schematic diagrams takenalong the lines A-A′ and B-B′ in FIG. 4A, respectively. Note that, forthe sake of simplification, illustrations of the conductive wires LW areomitted.

It can be understood that, from the back surface of the gas sensor 1illustrated in FIG. 4A, that is, a surface on the upper side in thecross-sectional schematic diagrams illustrated in FIGS. 4B and 4C, theback surface of the die pad portion 41, the back surfaces of theterminal portions 42, the back surface of the light receiving element10, the back surface of the light emitting element 20, and the sealingmember 80 are exposed.

This configuration is sometimes preferable because the die pad portion41 being exposed between the light receiving element 10 and the lightemitting element 20 on the back surface of the gas sensor 1 asillustrated in FIGS. 4A to 4C and forming the die pad portion 41, usinga conductive material having a high reflectance enable infrared raysemitted from the light emitting element 20 to reach the light receivingelement 10 more efficiently in a form of the gas sensor 1 including alight path as described in a second embodiment, which will be describedlater.

When the gas sensor 1 is viewed in plan as illustrated in FIG. 2 , thegas sensor 1 has a structure in which the light receiving element 10 andthe light emitting element 20 are surrounded by the second region 41(R2)of the die pad portion 41 and a structure in which the integratedcircuit 30 is arranged on the second region 41(R2) of the die padportion 41. Hence, forming the die pad portion 41, that is, the leadframe 40, using a material having a high thermal conductivity causestemperature inside the package to be uniformized. Thus, temperaturecharacteristics compensation with higher precision becomes possible, andconcentration measurement with higher precision becomes possible. Whenthe gas sensor 1 is embodied in a form of measuring temperature in thepackage, using diode characteristics inside the integrated circuit 30,effect of temperature inside the package being uniformized is caused toemerge more effectively.

The integrated circuit 30 is not particularly limited, provided that theintegrated circuit 30 is electrically connected to the light receivingelement 10 and at least one of the terminal portions 42. The integratedcircuit 30 preferably include at least one, and preferably all, of (1) acircuit configured to store calibration parameters of respective units,such as the light receiving element 10 and the light emitting element20, that require calibration and capable of outputting the calibrationparameters, (2) a circuit configured to amplify a signal from the lightreceiving element 10 and subject the signal to AD conversion, (3) acircuit configured to output a driving signal that drives the lightemitting element 20, (4) a circuit configured to perform intermittentdrive control of the light receiving element 10 and the light emittingelement 20, and (5) an interface circuit to an external instrument (suchas a signal processing circuit).

The gas sensor 1 configured in this manner drives the light emittingelement 20 and receives light radiated from the light emitting element20, using the light receiving element 10 in a space in which gas theconcentration of which is to be measured is present and, after havingperformed calibration and the like of parameter signals relating to thelight receiving element 10, the light emitting element 20, and the likeon the received signal, using the integrated circuit 30, outputs thecalibrated signal to an external instrument as a sensor signal, and theexternal instrument performs concentration calculation and the like ofthe gas to be measured, based on the sensor signal.

Advantageous Effects of First Embodiment

The gas sensor 1 according to the first embodiment includes theconfiguration illustrated in FIGS. 1, 2, 3A to 3D, and 4A to 4C.Therefore, the die pad portion 41 that has excellent heat conductionenables temperature of the light receiving element 10, the lightemitting element 20, and the integrated circuit 30 in the package to beuniformized. As a result, calibrating a parameter signal reflectingcharacteristics of at least one of the respective units, such as thelight receiving element 10 and the light emitting element 20, based onthe temperature of the integrated circuit 30 enables temperaturecharacteristic compensation to be performed with higher precision, and,consequently, it is possible to perform concentration measurement withhigher precision.

In addition, the die pad portion 41 having the first regions 41(R1),which have the first thickness, and the second region 41(R2), which hasthe second thickness thinner than the first thickness, and theintegrated circuit 30 being arranged on the second region 41(R2), thethickness of which is thin, while enabling miniaturization, enable highprecision measurement.

Not only does performing calibration based on the temperature of theintegrated circuit 30 in the package enable temperature characteristiccompensation to be performed, but also incorporating an integratedcircuit, which is generally disposed externally, into the same packageenables the entire gas sensor 1 to be miniaturized.

Since the light emitting element 20 is neither electrically connecteddirectly to the light receiving element 10 nor to the integrated circuit30, the gas sensor 1 has a high degree of freedom in layout, and it ispossible to increase precision of temperature characteristiccompensation caused by a layout and to achieve the gas sensor 1 that isfurther miniaturized.

Second Embodiment

Next, a second embodiment of the present invention will be described.

FIGS. 5A and 5B are schematic diagrams of a gas sensor 1 a according tothe second embodiment, and the gas sensor 1 a is configured by furtherdisposing a light reflection portion 60 that has a dome-shaped cavityportion 60 a on the inside thereof, on the back surface side of the gassensor 1 illustrated in FIGS. 4A to 4C.

The light reflection portion 60 is formed in a rectangularparallelepiped shape when viewed in plan, and the rectangularparallelepiped shape is formed with a width that causes second regions42(R2) and portions on the second region 42(R2) side of first regions42(R1) of respective terminal portions 42 to be covered and a lengththat causes the whole of first regions 41(R1) of a die pad portion 41 tobe covered. The light reflection portion 60 has, on the inside thereof,a reflecting surface 60 b the surface of which facing a light receivingsurface of a light receiving element 10 and a light emitting surface ofa light emitting element 20 is an ellipsoid and that is formed in a domeshape, and the cavity portion 60 a is formed in a size that causes thelight receiving element 10 and the light emitting element 20 to becontained within the cavity portion 60 a when viewed from the backsurface side. A material of a portion formed as the reflecting surface60 b of the light reflection portion 60 is preferably a metal or amultilayered dielectric material.

Note that, although, in the present embodiment, a single integratedcircuit 30 is also arranged on a second region 41(R2) of the die padportion 41, the gas sensor 1 may include a plurality of integratedcircuits 30 and the plurality of integrated circuits 30 may be arrangedon the second region 41(R2) of the die pad portion 41.

Note that the whole shape of the light reflection portion 60 may be anyshape, provided that the light reflection portion 60 has a dome-shapedreflecting surface 60 b.

In the light reflection portion 60, a not-illustrated vent thatpenetrates the light reflection portion 60 is formed, and it isconfigured such that, through the vent, gas to be measured is introducedinto the cavity portion 60 a and the gas to be measured is alsoexhausted to the outside of the cavity portion 60 a. The gas sensor 1 a,based on a detection signal detected by the light receiving element 10with gas to be measured having been introduced into the cavity portion60 a, performs predetermined processing in the integrated circuit 30 andoutputs a signal matching the detection signal, and a not-illustratedexternal device that is electrically connected to the integrated circuit30 performs concentration calculation and the like, based on thedetection signal input from the integrated circuit 30.

As described above, in the second embodiment, the light reflectionportion 60 having the dome-shaped reflecting surface 60 b on the insidethereof is formed. This configuration is sometimes preferable because,as a result of the configuration, it is possible to facilitate guidinginfrared rays emitted from the light emitting element 20 to the lightreceiving element 10. In addition, forming the die pad portion 41 of aconductive material having a high reflectance enables infrared raysemitted from the light emitting element 20 to reach the light receivingelement 10 more efficiently.

Variation of Second Embodiment

FIGS. 6A to 6C are schematic diagrams illustrative of a variation of thegas sensor 1 a according to the second embodiment, and the variation isconfigured by further including an optical member 70 and a mountingboard 100 in the gas sensor 1 a, which includes the light reflectionportion 60, illustrated in FIGS. 5A and 5B. FIG. 6A is a schematicdiagram when a gas sensor 1 b in the variation is viewed from a surfaceon the opposite side to the light reflection portion 60, that is, theback surface side, and FIGS. 6B and 6C are cross-sectional schematicdiagrams taken along the lines D-D′ and E-E′ in FIG. 6A, respectively.

The optical member 70 is constituted by a filter block that is anot-illustrated optical filter the side surfaces of which are covered bya sealing portion. The optical filter has a function of transmittinglight within a desired wavelength range selectively (that is, with hightransmittance). As a material of which an optical member constitutingthe optical filter is made, a material, such as silicon (Si) and glass(SiO₂), that transmits light within a preset wavelength range is used.However, without being limited to the configuration, the optical filtermay have a configuration in which a thin film is disposed on an opticalmember by means of vapor deposition or the like or may be a dielectricmultilayer film filter that is formed by stacking dielectric materialshaving different refractive indices in a multilayer form on an opticalmember.

As illustrated in FIG. 6A, the optical member 70 is formed in asubstantially square shape when viewed from the back surface side, oneside of the optical member 70 has a length equal to a distance betweenthe outer edges of two projecting portions 41 b of the die pad portion41, and the optical member 70 is arranged in such a way that boundariesbetween the first regions 41(R1) and the second regions 41(R2) ofprojecting portions 41 b, which are disposed at an edge on the lightemitting element 20 side of the die pad portion 41, and the one side ofthe optical member 70 overlap each other when viewed from the backsurface side and the optical member 70 further overlaps the lightemitting element 20.

This configuration is sometimes preferable because including the opticalmember 70 as illustrated in FIGS. 6A to 6C enables light emission and/orlight reception of infrared rays having specific wavelength to beachieved easily.

Note that, although FIGS. 6A to 6C illustrate an example in which theoptical member 70 is arranged on the light emitting element 20 side, theoptical member 70 may be arranged on the light receiving element 10side.

In addition, the optical member 70 may directly cover the surface of thelight emitting element 20 or the light receiving element 10 or mayindirectly cover the surface of the light emitting element 20 or thelight receiving element 10 with another substance or space interposedtherebetween. In other words, the optical member 70 is only required tobe arranged in a light path along which light having been emitted fromthe light emitting element 20 travels until the light is incident on thelight receiving element 10.

The mounting board 100 is larger than the package integrated by thesealing member 80 and includes mounting terminals 110 at locationsfacing the first regions 42(R1) of the terminal portions 42. FIGS. 6A to6C illustrate a case where the mounting board 100 includes in totalsixteen mounting terminals 110 that are composed of eight mountingterminals 110 on each of the right side and the left side. Each of themounting terminals 110 is to be electrically connected to the firstregion 42(R1) of one of the terminal portions 42 via a metal bump 200(FIG. 6C). Note that, although not illustrated, it is preferable that,by electrically connecting the mounting board 100 and the terminalportions 42 to each other via the metal bumps 200, the light emittingelement 20 be electrically connected to the integrated circuit 30 viathe mounting board 100.

Third Embodiment

Next, a third embodiment of the present invention will be described.

FIG. 7 is planar schematic diagram illustrative of an example of a gassensor 1 c according to the third embodiment. Note that, in FIG. 7 ,illustrations of conductive wires LW and a sealing member 80 areomitted.

The gas sensor 1 c according to the third embodiment differs from thegas sensor 1 according to the first embodiment illustrated in FIG. 1 inthe shapes of first regions and a second region of a die pad portion 41.Specifically, while, in the gas sensor 1 illustrated in FIG. 1, aboundary line BL serving as a boundary between one of the first regions41(R1) and the second region 41(R2) of the die pad portion 41 is onestraight line when viewed in plan, a boundary line BL between one offirst regions 41 ba(R1) and a second region 41 aa (R2) of the die padportion 41 is, instead of one straight line, composed of three linesegments, in FIG. 7 . In other words, although the die pad portion 41includes a rectangular portion 41 a and projecting portions 41 b, eachof the first regions 41 ba(R1) of the die pad portion 41 is composed ofa projecting portion 41 b and a portion of the rectangular portion 41 athat continues from the projecting portion 41 b, and forms a region thathas a rectangular shape formed by extending the projecting portion 41 bwhen viewed in plan and that has a first thickness. In other words, asillustrated in FIG. 7 , in the die pad portion 41, a boundary betweeneach of the first regions 41 ba(R1), which have the first thickness, andthe second region 41 aa(R2), which has a second thickness thinner thanthe first thickness, is composed of three line segments along threesides of an end on the second region 41 aa(R2) side of the first region41 ba(R1) and is formed in such a way that the three sides of the end ofthe first region 41 ba(R1) are surrounded by the second region 41aa(R2).

This configuration enables shape stability of the second region 41aa(R2) of the die pad portion 41 and positional stability at the time ofprocess thereof to be improved and arrangement of a light receivingelement 10 and a light emitting element 20 at locations as designed tobe facilitated, as a result of which the gas sensor 1 c can contributeto improvement in measurement precision.

Note that, although it is only required that, with respect to at leastone projecting portion 41 b among the four projecting portions 41 b ofthe die pad portion 41, the projecting portion 41 b and a portion of therectangular portion 41 a form the first region 41 ba (R1) and a boundaryline BL between the first region 41 ba(R1) and the second region 41aa(R2) be formed by a plurality of straight lines, it is preferable thateach of the four projecting portions 41 b and a portion of therectangular portion 41 a of the die pad portion 41 form one of the firstregions 41 ba (R1) and a boundary line BL between each of the firstregions 41 ba (R1) and the second region 41 aa(R2) be formed by, insteadof one straight line, a plurality of straight lines. In addition, eachof the boundary lines BL does not necessarily have to be a straightline, and it is only required that the second region 41 aa(R2) be formedin such a way as to surround the periphery of the end of each of thefirst regions 41 ba(R1).

Note that, although, in the present embodiment, one integrated circuit30 is also arranged on the second region 41 aa(R2) of the die padportion 41, the gas sensor 1 c may include a plurality of integratedcircuits 30 and the plurality of integrated circuits 30 may be arrangedon the second region 41 aa(R2) of the die pad portion 41.

From a viewpoint of increasing contribution to improvement inmeasurement precision, it is preferably configured such that, as the gassensor 1 c illustrated in FIG. 7 , some of line segments constituting asmallest convex polygon CP among convex polygons containing the whole ofthe second region 41 aa(R2) of the die pad portion 41 therewithin whenviewed in plan intersect the first regions 41 ba(R1) of the die padportion 41. This configuration enables the stability of the secondregion 41 aa (R2) of the die pad portion 41 to be further improved, as aresult of which measurement precision is further improved. Asillustrated in FIGS. 6A to 6C in the second embodiment, when the gassensor 1 c is mounted on the mounting board 100, the first regions 41 ba(R1) are preferably electrically connected to the mounting board 100 asterminal portions. Use of the metal bumps 200 that have excellent heatconduction enables temperature of the die pad portion 41 to be made moreuniform.

Fourth Embodiment

Next, a fourth embodiment of the present invention will be described.

FIG. 8 is planar schematic diagram illustrative of an example of a gassensor 1 d according to the fourth embodiment. Note that, in FIG. 8 , anillustration of a sealing member is omitted.

The gas sensor 1 d according to the fourth embodiment differs from thegas sensor 1 according to the first embodiment illustrated in FIG. 2 inthe shape of a terminal portion 42L among a plurality of terminalportions 42. The gas sensor 1 d also differs from the gas sensor 1 inthe shape of a rectangular portion 41 aL of a die pad portion 41 inconformity with the shape of the terminal portion 42L.

Specifically, as illustrated in FIG. 8 , the rectangular portion 41 aLof the die pad portion 41 is formed with the gas sensor 1 d placed insuch a manner that an edge on the light emitting element 20 side and anedge on the light receiving element 10 side are placed on the upper sideand the lower side when viewed in plan, respectively, and therectangular portion 41 aL has a notched portion 41 aL1 and a firstregion 41 aL(R1), which has a first thickness, formed on the right edgeside and the left edge side, respectively, of a location that is alocation between the light emitting element 20 and an integrated circuit30 and is a location slightly on the light emitting element 20 side of acentral portion in the longitudinal direction of the rectangular portion41 aL.

Note that, although, in the present embodiment, one integrated circuit30 is also arranged on a second region 41(R2) of the die pad portion 41,the gas sensor 1 d may include a plurality of integrated circuits 30 andthe plurality of integrated circuits 30 may be arranged on the secondregion 41(R2) of the die pad portion 41. In this case, it is preferableto form a first region having the first thickness in at least a portionof an interspace between the plurality of integrated circuits 30 whenviewed in plan, in respect of durability.

In addition, in the present embodiment, a second region having a secondthickness may be formed in the first region 41 aL(R1), which has thefirst thickness, and an integrated circuit 30 is further arranged in thesecond region.

In addition, the shape of the terminal portion 42L that faces thenotched portion 41 aL1 and that is located third from an edge on thelight emitting element 20 side of the gas sensor 1 d among eightterminal portions 42 arranged on the right edge side of the gas sensor 1d and the shape of the terminal portion 42LL that faces the first region41 aL(R1) of the die pad portion 41 and that is located third from theedge on the light emitting element 20 side among eight terminal portions42 arranged on the left edge side of the gas sensor 1 d are differentfrom those of the other terminal portions 42.

As illustrated in FIG. 8 , when viewed in plan, the terminal portion 42Lincludes a region 42L(D2) that is formed by extending a terminal portion42 in a second direction (D2), the second direction (D2) being adirection pointing to the die pad portion 41 aL, and a region 42L(D1)that extends in a first direction (D1), the first direction (D1) beingorthogonal to the second direction (D2), and has a shape that bends inthe shape of the letter L of the alphabet. Note that the first direction(D1) does not necessarily have to be orthogonal to the second direction(D2) and the two directions may form a shape in which the two directionintersect each other and that bends obliquely. That is, a second region42L(R2)b is only required to be arranged close to the integrated circuit30. As used herein, the term “intersect” means that two or more linesegments intersect one another at a point and is not a term that meansonly a form in which the line segments perpendicularly intersect oneanother.

In addition, the terminal portion 42L, as with the terminal portions 42,includes a first region 42L(R1)a that has the first thickness and asecond region 42L(R2)a that has the second thickness in this order fromthe right edge side of the gas sensor 1 d. Further, the terminal portion42L includes a first region 42L(R1)b that continues from the secondregion 42L(R2)a and that has the first thickness and a second region42L(R2)b that continues from the first region 42L(R1)b and that has thesecond thickness. The first region 42L(R1)b includes a region thatcontinues from the second region 42L(R2)a and that extends to the end inthe second direction and a region occupying approximately one-eighth ofthe whole of a region that continues from the region extending to theend in the second direction and that extends in the first direction. Thesecond region 42L(R2)b includes a region that is the region extending inthe first direction excluding the first region 42L(R1)b. The secondregion 42L(R2)b, which has the second thickness, forms a bonding region42L(R3).

On the other hand, the terminal portion 42LL has a shape in which asecond region 42(R2) in a terminal portion 42 extends, includes a firstregion 42LL(R1) and a second region 42LL(R2) that continues from thefirst region 42LL(R1) and that has the second thickness, and has the endof the second region 42LL(R2) on the opposite side to the first region42LL(R1) continuing to the first region 41 aL(R1), which is formed onthe rectangular portion 41 aL and has the first thickness.

The form illustrated in FIG. 8 is sometimes preferable because the formenables layout of electrical connections via conductive wires LW to befacilitated and the whole of the gas sensor 1 d to be miniaturized. Inother words, as illustrated in FIG. 8 , the terminal portion 42L has theend on the die pad portion 41 side extended to a vicinity of a centralportion in the width direction of the die pad portion 41. Thus,disposing a terminal at an edge portion on the light emitting element 20side of the integrated circuit 30 and connecting the terminal to thesecond region 42L(R2)b, which is the bonding region 42L(R3), of theterminal portion 42L, using a conductive wire LW enable the wiring to beperformed using a short conductive wire LW and routing of wires to beeasily performed.

In addition, the first region 41 aL(R1) is disposed on the opposite sideto the notched portion 41 aL1 of the rectangular portion 41 aL, and thefirst region 41 aL(R1) has a thickness thicker than the thickness of thesecond region 41(R2). This configuration enables reduction in stabilityof the rectangular portion 41 a due to the disposition of the notchedportion 41 aL1 to be suppressed.

In the terminal portion 42L, the region extending in the seconddirection preferably includes regions the thicknesses of which aredifferent from one another. Specifically, as illustrated in FIG. 8 , aportion of the region extending in the second direction is preferablythe second region 42L(R2) a the thickness of which is thinner than thatof a first region. This configuration enables sealing resin to flowsmoothly, misalignment of the light receiving element 10 and the lightemitting element 20 to be suppressed, and deterioration in measurementprecision to be suppressed when a lead frame 40, the light receivingelement 10, the light emitting element 20, and the integrated circuit 30are sealed with the sealing member 80 by molding. Note that, since thesecond region 42L(R2)a is disposed for the purpose of causing sealingresin to flow smoothly, the second region 42L(R2)a does not necessarilyhave to have the second thickness and is only required to have athickness thinner than the first thickness. From a viewpoint of causingsealing resin to flow smoothly, the second region 42L(R2)a preferablyhas a thickness equal to the thickness of the second regions 42(R2) ofthe other terminal portions 42.

Variation of Fourth Embodiment

FIG. 9 is planar schematic diagram illustrative of an example of a gassensor 1 e in the fourth embodiment. The gas sensor 1 e is configuredsuch that, in the gas sensor 1 d illustrated in FIG. 8 , two terminalportions 42L1 and 42L2 that face a notched portion 41 aL1 and that arelocated adjacent to each other include regions 42L1 (D2) and 42L2 (D2)that extend in the second direction (D2), respectively and, further,both the ends of the regions 42L1(D2) and 42L2(D2) are connected to aregion 42L12 (D1) that extends in the first direction (D1).

In addition, the terminal portion 42L1, as with terminal portions 42,includes a first region 42L1(R1)a that has the first thickness and asecond region 42L1(R2)a that has the second thickness in this order fromthe right edge side of the gas sensor 1 e and further includes a firstregion 42L1(R1)b and a second region 42L1(R2)b that has the secondthickness. Likewise, the terminal portion 42L2, as with the terminalportions 42L1, includes a first region 42L2(R1)a that has the firstthickness and a second region 42L2(R2)a that has the second thickness inthis order from the right edge side of the gas sensor 1 e and furtherincludes a first region 42L2(R1)b and a second region 42L2(R2)b that hasthe second thickness.

The region 42L12(D1) includes a first region 42L12(R1) that has thefirst thickness and a second region 42L12(R2) that continues from thefirst region 42L12 (R1) and that has the second thickness.

This configuration is sometimes preferable because forming the twoterminal portions 42L1 and 42L2, which face the notched portion 41 aL1,in the shapes illustrated in FIG. 9 enables shape stability to beimproved. In addition, in FIG. 9 , second regions (42L1(R2)a, 42L1(R2)b,42L2(R2)a, and 42L2(R2)b) that have a thickness thinner than thethickness of the first regions R1 are formed at two locations on each ofthe regions 42L1(D2) and 42L2(D2), which extend in the second direction.This configuration is sometimes preferable because the configurationenables a dead end between the two regions 42L1(D2) and 42L2(D2)extending in the second direction to be opened and effect of causingsealing resin to flow smoothly to emerge.

[Manufacturing Method]

Next, an example of a method for manufacturing the gas sensor 1according to the present embodiment will be described. A method formanufacturing the gas sensor 1 according to the first embodiment will bedescribed below using FIGS. 10A to 10D. FIGS. 10A to 10D arecross-sectional schematic diagrams taken along the line F-F′ in FIG. 1 .

First, on a heat-resistant tape 201, a lead frame 40 that has beensubjected to patterning and half-etching and in which a die pad portion41 that includes a first regions 41(R1) having the first thickness and asecond region 41(R2) having a thickness thinner than the first regions41(R1) and terminal portions 42 are formed is arranged (FIG. 10A). Inorder to facilitate wire bonding, which will be described later, thesurface of the lead frame 40 may be subjected to plating.

Subsequently, a light receiving element 10 and a light emitting element20 are arranged in regions (a light receiving element arrangement region41 c and a light emitting element arrangement region 41 d) surrounded bya second region 41(R2) of the die pad portion 41 on the heat-resistanttape 201 via an adhesive layer of the heat-resistant tape 201, anintegrated circuit 30 is arranged on the second region 41(R2) of the diepad portion 41 preferably via an adhesive agent or a film having highthermal conductivity, and the light receiving element 10 and theintegrated circuit 30, the light emitting element 20 and second regions42(R2) of respective terminal portions 42, and the integrated circuit 30and second regions 42(R2) of respective terminal portions 42 arerespectively wire-bonded to each other, using conductive wires LW (FIG.10B). In FIG. 10B, for the sake of simplification, a conductive wire LWconnecting the light receiving element 10 and the integrated circuit 30to each other and a conductive wire LW connecting the light emittingelement 20 and the second region 42(R2) of a terminal portion 42 to eachother are illustrated.

Subsequently, a lower mold 203 is arranged on the side where theheat-resistant tape 201 is arranged, an upper mold 202 is arranged onthe opposite side to the side where the heat-resistant tape 201 isarranged, and sealing resin that serves as a sealing member 80 isinjected into a space sandwiched between the heat-resistant tape 201 andthe upper mold 202 (FIG. 10C).

Subsequently, the upper mold 202 and the lower mold 203 are removed, andthe heat-resistant tape 201 is also removed. By dicing a region havingkerf width W, using a dicing apparatus and individual pieces beingthereby cut out and being turned over, the gas sensor 1 on the uppersurface side of which portions of the light receiving element 10 and thelight emitting element 20 are exposed is obtained (FIG. 10D).

Although the embodiments of the present invention were described above,the above-described embodiments indicate devices and methods to embodythe technical idea of the present invention by way of example, and thetechnical idea of the present invention does not limit the materials,shapes, structures, arrangements, and the like of the constituentcomponents. The technical idea of the present invention can be subjectedto a variety of alterations within the technical scope prescribed by theclaims described in CLAIMS.

REFERENCE SIGNS LIST

-   1, 1 a to 1 e Gas sensor-   10 Light receiving element-   20 Light emitting element-   30 Integrated circuit-   40 Lead frame-   41 Die pad portion-   41 a, 41 aL Rectangular portion-   41 aL1 Notched portion-   41 b Projecting portion-   41(R1), 41 ba(R1), 41 aL(R1) First region of a die pad portion-   41(R2), 41 aa(R2) Second region of a die pad portion-   42, 42L, 42L1, 42L2, 42LL Terminal portion-   42(R1), 42L1(R1) First region of a terminal portion-   42(R2), 42L2(R2) Second region of a terminal portion-   60 Light reflection portion-   60 a Cavity portion-   60 b Reflecting surface-   70 Optical member-   80 Sealing member-   100 Mounting board-   110 Mounting terminal-   200 Metal bump-   BL Boundary line-   LW Conductive wire

The invention claimed is:
 1. A gas sensor comprising: a light receiving element; a light emitting element; an integrated circuit; a lead frame; and a sealing member configured to seal the light receiving element, the light emitting element, the integrated circuit, and the lead frame into a package, wherein the lead frame includes at least one die pad portion and a plurality of terminal portions, wherein at least the die pad portion includes a first region having a first thickness and a second region having a second thickness thinner than the first thickness, the integrated circuit is arranged on the second region of the die pad portion, the light emitting element is neither electrically connected directly to the light receiving element nor to the integrated circuit and is electrically connected to at least one of the plurality of terminal portions, the light receiving element is electrically connected to the integrated circuit and is arranged on an opposite side to the light emitting element with the integrated circuit interposed between the light receiving element and the light emitting element, and the integrated circuit is electrically connected to at least one of the plurality of terminal portions.
 2. The gas sensor according to claim 1, wherein the light receiving element is electrically connected to the integrated circuit via a conductive wire.
 3. The gas sensor according to claim 1, wherein the light emitting element and the integrated circuit are mounted on a mounting board, and the light emitting element is electrically connected to the integrated circuit via the mounting board.
 4. The gas sensor according to claim 1, wherein the first region of the die pad portion is arranged at a periphery of the second region and is arranged in such a way that the second region surrounds a portion of an end of the first region.
 5. The gas sensor according to claim 4, wherein a plurality of the first regions of the die pad portion are arranged in such a way that the second region surrounds portions of ends of the first regions.
 6. The gas sensor according to claim 5, wherein, when viewed in plan, some of line segments constituting a smallest convex polygon including a whole of the second region of the die pad portion within the convex polygon intersect the first regions of the die pad portion.
 7. The gas sensor according to claim 1, wherein the plurality of terminal portions are arranged in a line along the die pad portion on both sides of the die pad portion with the die pad portion interposed between the terminal portions, at least one terminal portion among terminal portions electrically connected to the integrated circuit includes a region extending in a second direction, the second direction intersecting a direction in which the plurality of terminal portions are lined, and a region extending in a first direction, the first direction intersecting the second direction and coming close to the integrated circuit, between the integrated circuit and the light emitting element and includes a bonding region at a tip of the region extending in the first direction, and the integrated circuit and the bonding region are connected to each other by a conductive wire.
 8. The gas sensor according to claim 7, wherein each of a plurality of terminal portions among terminal portions electrically connected to the integrated circuit includes a region extending in the second direction, and a region extending in the second direction of each of the plurality of terminal portions including regions extending in the second direction is connected to a common region extending in the first direction.
 9. The gas sensor according to claim 7, wherein a region extending in the second direction includes, in the region, regions having different thicknesses.
 10. The gas sensor according to claim 1, wherein each of the terminal portions has the first region and the second region, and the gas sensor includes a first surface on which only a portion of each of the plurality of terminal portions, a portion of the die pad portion, and a portion of the sealing member are exposed.
 11. The gas sensor according to claim 1, wherein each of the terminal portions has the first region and the second region, and the gas sensor includes a second surface on which only a portion of each of the plurality of terminal portions, a portion of the die pad portion, a portion of the light receiving element, a portion of the light emitting element, and a portion of the sealing member are exposed.
 12. The gas sensor according to claim 11, comprising: a light reflection portion internally including a cavity portion covering at least a portion of the second surface.
 13. The gas sensor according to claim 11, further comprising: an optical member arranged in such a manner as to directly or indirectly cover an exposed portion of at least either the light emitting element, a portion of which is exposed, or the light receiving element, a portion of which is exposed, and configured to transmit light having a desired wavelength.
 14. The gas sensor according to claim 1, wherein the integrated circuit is electrically connected to at least one of the plurality of terminal portions via a conductive wire.
 15. The gas sensor according to claim 14, wherein the terminal portion to which the conductive wire is connected among the plurality of terminal portions includes a bonding region, and a thickness of the bonding region is thinner than the first thickness.
 16. The gas sensor according to claim 15, wherein the bonding region has plating on a surface of the bonding region, and the conductive wire is directly connected to the plating.
 17. The gas sensor according to claim 1, wherein the integrated circuit outputs a control signal for controlling the light emitting element and, when a signal from the light receiving element is input, performs amplification and AD conversion. 